This invention relates to a web drive apparatus for transport of various information media in peripheral units and/or terminal units of an electronic computer.
Apparatus for driving a web such as a magnetic tape of a magnetic tape recording and reproducing apparatus have hitherto been known as disclosed in U.S. Pat. Nos. 3,781,490 and 3,912,144. In this type of apparatus, a web is wound around two web reels each driven by a separate motor, the web is transported when the web reels are driven and rotated by the motors, and information is transmitted to or from the web for recording or reproducing through an information exchange station such as magnetic head, disposed between the web reels.
Such a web drive apparatus is required to provide capability of high-speed access and highly accurate positioning. In high-speed drive of the web made of a visco-elastic material, however, a problem of transient vibrations of the web is encountered. Generation of transient vibrations of the web is more frequent in intermittent transport of the web than in constant speed transport of the web because rapid acceleration and deceleration of the web are intermittently repeated in a short time. Under the influence of transient vibrations of the web, the web may fail to be correctly positioned relative to the information exchange station even if the web is wound correctly on the take-up reel. This prevents information from being transmitted correctly to or from the intended portion of the web and thus preventing high-density recording of information on the web. Expecially the adverse affect due to transient vibrations of the web is aggravated in the case of an information exchange station using a rotary head in which information transmission through the station continues over a relatively long distance on the track across the web.